This invention relates to a process and apparatus for increasing the size of ammonium sulfate crystals, e.g., from an average size of about 0.5 mm to an average size of at least about 1.0 mm.
The manufacture of ammonium sulfate is an important industrial process and is the subject of a considerable body of patent and non-patent literature. See, e.g., U.S. Pat. Nos. 1,266,212; 1,919,707; 2,043,067; 2,092,073; 2,099,079; 2,102,107; 2,178,082; 2,226,101; 2,228,742; 2,368,901; 2,423,794; 2,424,207;. 2,599,067; 2,631,084; 2,659,659; 2,782,097; 2,795,487; 2,805,125; 2,874,028; and 2,895,800, and Parkash, "Residence Times of Crystals in a Fluidised Bed Crystallizer", Chemistry and Industry, pp. 919-920, Jun. 3, 1967; Parkash et al., "Crystal Growth in Fluidized Beds", Indian Chemical Engineer, pp. 3-6, January, 1968; Vragov, "Investigation of Ammonium Sulfate Crystallization in a Pseudo Liquified Layer", Sb. Nauch, Tr., Kuzbas Politekh Int., No. 26, 1970; and, Postnikov et al., "Crystallization of Ammonium Sulfate in a Two-Circuit Device With a Circulating Suspension", Koksii Khimiya, No. 4, pp. 24-27, 1983.
It has long been recognized that the tendency of ammonium sulfate crystals to cake on standing is lessened with increased size of the crystals. It has therefore been a goal of many of these manufacturing processes to provide ammonium sulfate crystals of larger size, e.g., averaging at least about 1.0 mm. Typically, such increased crystal size has been achieved through control of the crystallization process.